An outstanding problem in quantum optics is how light interacts with atoms inside an optical cavity. In the strong-coupling regime—where the coupling between an atom and the cavity field dominates the rate with which the field leaks out of the cavity and that of spontaneous emission—a single atom can significantly affect the field, and the presence of a single photon can strongly affect the atom.

In a paper published in Physical Review A, Fam Le Kien and K. Hakuta, both at the University of Electro-Communications in Japan, analyze how nanofibers—fibers stretched thin with core diameters smaller than a wavelength—may complement atom-cavity technology. They study a nanofiber that combines with two built-in fiber Bragg grating (FBG) mirrors to form a cavity. A surrounding atom interacts with the optical field, confined in the transverse direction by the narrow fiber and in the longitudinal direction by the gratings. As a result, the dynamics of the mean number of photons closely tracks the translational motion of the atom traversing the standing-wave field formed by the two FBG mirrors.

This work may lead to applications in fiber optics, cavity quantum electrodynamics, cold and ultracold atoms, and quantum optics effects such as electromagnetically induced transparency. – Frank Narducci

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